Semiconductor memory devices, memory systems including the same and methods of operating memory systems

ABSTRACT

A semiconductor memory device includes a memory cell array, an error correction circuit, an error log register and a control logic circuit. The memory cell array includes a plurality of memory bank arrays and each of the memory bank arrays includes a plurality of pages. The control logic circuit is configured to control the error correction circuit to perform an ECC decoding sequentially on some of the pages designated at least one access address for detecting at least one bit error, in response to a first command received from a memory controller. The control logic circuit performs an error logging operation to write page error information into the error log register and the page error information includes a number of error occurrence on each of the some pages determined from the detecting.

CROSS-REFERENCE TO RELATED APPLICATIONS

This U.S. application is a continuation application of U.S. patentapplication Ser. No. 15/238,216 filed Aug. 16, 2016, which claimspriority under 35 USC § 119 to Korean Patent Application No.10-2015-0160106, filed on Nov. 16, 2015, in the Korean IntellectualProperty Office, the disclosures of which are incorporated by referencein their entirety herein.

BACKGROUND 1. Technical Field

The present disclosure relates to memories, and more particularly tosemiconductor memory devices, memory systems including the same andmethods of operating memory systems.

2. Discussion of Related Art

Semiconductor memory devices may be classified into non-volatile memorydevices such as flash memory devices and volatile memory devices such asDynamic Random Access Memories (DRAMs). High speed operation and costefficiency of DRAMs make it possible for DRAMs to be used for computersystem memories.

Electrical or magnetic interference inside a computer system can cause asingle bit of a DRAM to spontaneously flip to the opposite state,resulting in a bit error. Further, when a specific address isintensively applied to the DRAM, data retention reliability of memorycells coupled to a word-line designated by the specific address maydegrade.

SUMMARY

According to an exemplary embodiment of the inventive concept, asemiconductor memory device includes a memory cell array, an errorcorrection circuit, an error log register and a control logic circuit.The memory cell array includes a plurality of memory bank arrays andeach of the memory bank arrays includes a plurality of pages. Thecontrol logic circuit is configured to control the error correctioncircuit to perform an error check and correction (ECC) decodingsequentially on some pages designated at least one access address fordetecting at least one bit error, in response to a first command from amemory controller. The control logic circuit performs an error loggingoperation to write page error information into the error log registerand the page error information includes a number of error occurrences oneach of the some pages determined from the detecting.

According to an exemplary embodiment of the inventive concept, a memorysystem includes the semiconductor memory device and the memorycontroller. The memory controller controls the at least onesemiconductor memory device.

According to an exemplary embodiment of the inventive concept, a methodof operating a memory system including a semiconductor memory device anda memory controller that controls the semiconductor memory device isprovided. The method includes the memory controller generating a commandand an access address, the semiconductor memory device performing anerror check and correction (ECC) decoding on some pages of the memorydevice designated by the access address for detecting at least one biterror, in response to the command, and the semiconductor memory deviceperforming an error logging operation to write page error informationinto the error log register, the page error information including anumber of error occurrences on each of the some pages determined fromthe detecting.

According to an exemplary embodiment of the inventive concept, asemiconductor memory device includes a memory cell array, a register,and a controller. The register stores storing error occurrence countsfor each page of a plurality of pages of the memory cell array. Thecontroller is configured to receive a command through a first pin of thesemiconductor memory device, receive an address through a second pin ofthe semiconductor memory device, receive data through a third pin of thesemiconductor memory device during a first mode, and output a signalincluding information of the register through the third pin to a memorycontroller during a second other mode.

BRIEF DESCRIPTION OF THE DRAWINGS

Exemplary embodiments of the inventive concept will be described belowin more detail with reference to the accompanying drawings.

FIG. 1 is a block diagram illustrating an electronic system according toan exemplary embodiment of the inventive concept.

FIG. 2 is a block diagram illustrating the memory system shown in FIG. 1according to an exemplary embodiment of the inventive concept.

FIG. 3 is a block diagram illustrating the semiconductor memory deviceshown in FIG. 2, according to an exemplary embodiment of the inventiveconcept.

FIGS. 4A to 4E are circuit diagrams of examples of the memory cell shownin FIG. 3, according to exemplary embodiments of the inventive concept.

FIG. 5 illustrates an example of the memory cell (referred to asSTT-MRAM cell) in FIG. 3 according to an exemplary embodiment of theinventive concept.

FIGS. 6A and 6B illustrate a magnetization direction according to datawritten to the MTJ element shown in FIG. 5.

FIG. 7 is a block diagram illustrating the memory controller in FIG. 2according to an exemplary embodiment of the inventive concept.

FIG. 8 illustrates a portion of the semiconductor memory device of FIG.3 in a normal mode.

FIG. 9 illustrates a bank array and the error correction circuit shownin the semiconductor memory device of FIG. 3.

FIG. 10 illustrates a portion of the semiconductor memory device of FIG.3 in an ECS mode.

FIG. 11 illustrates the error log register in the semiconductor memorydevice 200 of FIG. 3.

FIG. 12 illustrates the error correction circuit and the I/O gatingcircuit in the semiconductor memory device of FIG. 3 in the ECS mode.

FIG. 13 illustrates the error correction circuit and the I/O gatingcircuit in the semiconductor memory device of FIG. 3 in the normal mode.

FIG. 14 illustrates that a scrubbing operation is performed in thesemiconductor memory device of FIG. 10.

FIG. 15 illustrates the ECC encoder in the error correction circuit inFIG. 13.

FIG. 16 illustrates the ECC decoder in the error correction circuit inFIGS. 12 and 13.

FIG. 17 is a flow chart illustrating a method of operating asemiconductor memory device according to an exemplary embodiment of theinventive concept.

FIG. 18 is a flow chart illustrating the ECS operation in the method ofFIG. 17 according to an exemplary embodiment of the inventive concept.

FIG. 19 is a structural diagram illustrating a semiconductor memorydevice according to an exemplary embodiment of the inventive concept.

FIG. 20 illustrates the memory system of FIG. 2 in the ECS mode.

FIG. 21 is a flow chart illustrating a method of operating a memorysystem according to an exemplary embodiment of the inventive concept.

FIG. 22 illustrates a memory system including the semiconductor memorydevice according to an exemplary embodiment of the inventive concept.

FIG. 23 illustrates a memory system including the semiconductor memorydevice according to an exemplary embodiment of the inventive concept.

FIG. 24 is a block diagram illustrating a computing system including thesemiconductor memory device according to an exemplary embodiment of theinventive concept.

DETAILED DESCRIPTION

The inventive concept will be described more fully hereinafter withreference to the accompanying drawings, in which exemplary embodimentsthereof are shown. However, the present inventive concept may beembodied in many different forms and should not be construed as limitedto the exemplary embodiments set forth herein. It should also beemphasized that the present inventive concept provides details ofalternative examples, but such listing of alternatives is notexhaustive. Like numerals refer to like elements throughout.

It will be understood that when an element is referred to as being“connected” or “coupled” to another element, it can be directlyconnected or coupled to the other element or intervening elements may bepresent. As used herein, the singular forms “a,” “an” and “the” areintended to include the plural forms as well, unless the context clearlyindicates otherwise.

FIG. 1 is a block diagram illustrating an electronic system according toan exemplary embodiment of the inventive concept.

Referring to FIG. 1, an electronic system (or, an electronic device) 10includes a host 15 (e.g., a host device, a host computer, etc.) and amemory system 20. The memory system 20 includes a memory controller 100and a plurality of semiconductor memory devices 200 a˜200 n (n is aninteger greater than two). While FIG. 1 shows multiple semiconductormemory devices, there may only be a single semiconductor memory devicein an alternate embodiment.

The host 15 may communicate with the memory system 20 through variousinterface protocols such as Peripheral Component Interconnect-Express(PCI-E), Advanced Technology Attachment (ATA), Serial ATA (SATA),Parallel ATA (PATA), or serial attached SCSI (SAS). In addition, thehost 15 may also communicate with the memory system 20 through interfaceprotocols such as Universal Serial Bus (USB), Multi-Media Card (MMC),Enhanced Small Disk Interface (ESDI), or Integrated Drive Electronics(IDE).

The memory controller 100 may control overall operation of the memorysystem 20. The memory controller 100 may control overall data exchangebetween the host 15 and the plurality of semiconductor memory devices200 a˜200 n. For example, the memory controller 100 may write data intothe plurality of semiconductor memory devices 200 a˜200 n or read datafrom the plurality of semiconductor memory devices 200 a˜200 n inresponse to a request (e.g., a request message, a command, etc.) fromthe host 15. For example, the request may be a read request including aread command and an access address or a write request including a writecommand, an access address, and data to write. The read command and thewrite command may be referred to as access commands.

In addition, the memory controller 100 may apply operation commands tothe plurality of semiconductor memory devices 200 a˜200 n forcontrolling the plurality of semiconductor memory devices 200 a˜200 n.

In an embodiment, each of the plurality of semiconductor memory devices200 a˜200 n is a memory device including resistive type memory cellssuch as a magnetoresistive random access memory (MRAM), a resistiverandom access memory (RRAM), a phase change random access memory (PRAM)and a ferroelectric random access memory (FRAM), etc. In an exemplaryembodiment, each of the plurality of semiconductor memory devices 200a˜200 n includes dynamic memory cells such as a dynamic random accessmemory (DRAM).

An MRAM is a nonvolatile computer memory based on magnetoresistance. AnMRAM is different from a volatile RAM in many aspects. For example,since an MRAM is nonvolatile, the MRAM may retain all stored data evenwhen power is turned off.

Although a nonvolatile RAM is generally slower than a volatile RAM, anMRAM has read and write response times comparable with read and writeresponse times of a volatile RAM. Unlike a volatile RAM that stores dataas an electric charge, an MRAM stores data by using magnetoresistance(or magnetoresistive) elements. In general, a magnetoresistance elementis made of two magnetic layers, each having a magnetization.

An MRAM is a nonvolatile memory device that reads and writes data byusing a magnetic tunnel junction pattern including two magnetic layersand an insulating film disposed between the two magnetic layers. Aresistance value of the magnetic tunnel junction pattern may varyaccording to a magnetization direction of each of the magnetic layers.The MRAM may program or remove data by using the variation of theresistance value.

An MRAM using a spin transfer torque (STT) phenomenon uses a method inwhich when a spin-polarized current flows in one direction, amagnetization direction of the magnetic layer is changed due to the spintransfer of electrons. A magnetization direction of one magnetic layer(e.g., a pinned layer) may be fixed and a magnetization direction of theother magnetic layer (e.g., a free layer) may vary according to amagnetic field generated by a program current.

The magnetic field of the program current may arrange the magnetizationdirections of the two magnetic layers in parallel or in anti-parallel.In at least one exemplary embodiment, if the magnetization directions ofthe two magnetic layers are parallel, a resistance between the twomagnetic layers is in a low (“0”) state. If the magnetization directionsof the two magnetic layers are anti-parallel, a resistance between thetwo magnetic layers is in a high (“1”) state. Switching of themagnetization direction of the free layer and the high or low state ofthe resistance between the two magnetic layers result in write and readoperations of the MRAM.

Although the MRAM is nonvolatile and provides a quick response time, anMRAM cell has a limited scale and is sensitive to a write disturbancebecause the program current applied to switch the high and low states ofthe resistance between the magnetic layers of the MRAM is typicallyhigh. Accordingly, when a plurality of cells are arranged in an MRAMarray, a program current applied to one memory cell can inadvertentlychange a magnetic field of a free layer of an adjacent cell. Such awrite disturbance may be mitigated (or alternatively, prevented) byusing an STT phenomenon. A typical STT-MRAM may include a magnetictunnel junction (MTJ), which is a magnetoresistive data storage deviceincluding two magnetic layers (e.g., a pinned layer and a free layer)and an insulating layer disposed between the two magnetic layers.

A program current typically flows through the MTJ. The pinned layerspin-polarizes electrons of the program current, and a torque isgenerated as the spin-polarized electron current passes through the MTJ.The spin-polarized electron current applies the torque to the free layerwhile interacting with the free layer. When the torque of thespin-polarized electron current passing through the MTJ is greater thana threshold switching current density, the torque applied by thespin-polarized electron current is sufficient to switch a magnetizationdirection of the free layer. Accordingly, the magnetization direction ofthe free layer may be parallel or anti-parallel to the pinned layer anda resistance state in the MTJ is changed.

The STT-MRAM removes a requirement of an external magnetic field for thespin-polarized electron current to switch the free layer in themagnetoresistive device. In addition, the STT-MRAM improves scaling as acell size is reduced and the program current is reduced to mitigate (oralternatively, prevent) the write disturbance. In addition, the STT-MRAMmay have a high tunnel magnetoresistance ratio, which improves a readoperation in a magnetic domain by allowing a high ratio between the highand low states.

An MRAM is low cost and has high capacity (like a dynamic random accessmemory (DRAM), operates at high speed (like a static random accessmemory (SRAM), and is nonvolatile (like a flash memory).

FIG. 2 is a block diagram illustrating the memory system shown in FIG. 1according to an exemplary embodiment of the inventive concept.

In FIG. 2, only one semiconductor memory device 200 a in communicationwith the memory controller 100 is illustrated for convenience. However,the details discussed herein related to a semiconductor memory device200 a may equally apply to the other semiconductor memory devices 200b˜200 n.

Referring to FIG. 2, the memory system 20 includes the memory controller100 and the semiconductor memory device 200 a. Each of the memorycontroller 100 and the semiconductor memory device 200 a may be formedas a separate semiconductor chip or as a separate group of chips (e.g.,the memory controller 100 and the semiconductor memory device 200 a maybe packaged together in stack of the semiconductor chips).

The memory controller 100 and the semiconductor memory device 200 a areconnected to each other through corresponding command pins 101 and 201,corresponding address pins 102 and 202, corresponding data pins 103 and203 and corresponding separate pins 104 and 204. The command pins 101and 201 transmit a command signal CMD through a command transmissionline TL1, the address pins 102 and 202 transmit an address signal ADDRthrough an address transmission line TL2, and the data pins 103 and 203exchange main data MD in a normal mode and transmit an error informationsignal EIS in an error check and scrub (ECS) mode through a datatransmission line TL3. The separate pins 104 and 204 transmit an alertsignal ALRT to the memory controller 100 in the ECS mode.

The semiconductor memory device 200 a includes a memory cell array 300that stores the main data MD, an error correction circuit 400, an errorlog register 460 and a control logic circuit 210 (also referred to as a‘control logic’) that controls the error correction circuit 400. In anembodiment, a main controller includes the control circuit 210 and theerror correction circuit 400.

When the command CMD designates the ECS mode, the control logic circuit210 may control the error correction circuit 400 to perform an errorcheck and correction (ECC) decoding sequentially on each read data fromsome pages designated by address signal ADDR to generate an errorgeneration signal. The control logic circuit 210 may perform an errorlogging operation to write page error information in each row of theerror log register 460 and the page error information may include atleast a number of error occurrences on each of the some pages. When theCMD is a register read command RRD, the control logic circuit 210 mayprovide the memory controller 100 with all or part of the page errorinformation in the error log register 460 as the error informationsignal EIS.

FIG. 3 is a block diagram illustrating the semiconductor memory deviceshown in FIG. 2, according to an exemplary embodiment of the inventiveconcept.

Referring to FIG. 3, the semiconductor memory device 200 a includes thecontrol logic circuit 210, an address register 220, a bank control logic230, a refresh counter 297, a row address multiplexer 240, (‘RA MUX’) acolumn address latch 250 (‘CA LATCH’), a row decoder 260, a columndecoder 270, the memory cell array 300, a sense amplifier unit 285, aninput/output (I/O) gating circuit 290, the error correction circuit 400,a data input/output (I/O) buffer 299, and an error log register 460. Thecolumn address latch 250 may include one or more latch circuits. Thesense amplifier unit 285 may include one or more sense amplifiers.

In an embodiment, the refresh counter 297 is omitted from thesemiconductor memory device 200 a. That is, when the memory cell array300 is implemented with a plurality of resistive type memory cells, therefresh counter 297 is omitted from the semiconductor memory device 200a.

The memory cell array 300 includes first through fourth bank arrays310˜340. The row decoder 260 includes first through fourth bank rowdecoders 260 a˜260 d respectively coupled to the first through fourthbank arrays 310˜340. The column decoder 270 includes first throughfourth bank column decoders 270 a˜270 d respectively coupled to thefirst through fourth bank arrays 310˜340. The sense amplifier unit 285includes first through fourth bank sense amplifiers 285 a˜280 drespectively coupled to the first through fourth bank arrays 310˜340.Each of the first through fourth bank arrays 310˜340 may include aplurality of memory cells MC, and each of memory cells MC is coupled toa corresponding word-line WL and a corresponding bit-line BTL. The firstthrough fourth bank arrays 310˜340, the first through fourth bank rowdecoders 260 a˜260 d, the first through fourth bank column decoders 270a˜270 d and first through fourth bank sense amplifiers 285 a˜280 d mayform first through fourth banks. Although the semiconductor memorydevice 200 a shown in FIG. 3 illustrates four banks, the semiconductormemory device 200 a may have less than four banks or greater than fourbanks in other embodiments.

The address register 220 receives an address ADDR including a bankaddress BANK_ADDR, a row address ROW_ADDR and a column address COL_ADDRfrom the memory controller 100. The address register 220 provides thereceived bank address BANK_ADDR to the bank control logic 230, providesthe received row address ROW_ADDR to the row address multiplexer 240,and provides the received column address COL_ADDR to the column addresslatch 250. The address ADDR may be provided by the memory controller 100along with a command (e.g., a write or read) so that the command isapplied to an area of the memory cell array 300 with a locationcorresponding to the address ADDR.

The bank control logic 230 may generate bank control signals in responseto the bank address BANK_ADDR. One of the first through fourth bank rowdecoders 260 a˜260 d corresponding to the bank address BANK_ADDR may beactivated in response to the bank control signals, and one of the firstthrough fourth bank column decoders 270 a˜270 d corresponding to thebank address BANK_ADDR may be activated in response to the bank controlsignals.

The refresh counter 297 generates a refresh row address REF_ADDR forrefreshing memory cell rows in the memory cell array 300 under controlof the control logic circuit 210. The refresh counter 297 may beincluded when the memory cells MC are implemented with dynamic memorycells.

The row address multiplexer 240 receives the row address ROW_ADDR fromthe address register 220, and receives the refresh row address REF_ADDRfrom the refresh counter 297. The row address multiplexer 240selectively outputs the row address ROW_ADDR or the refresh row addressREF_ADDR as a row address RA. The row address RA that is output from therow address multiplexer 240 is applied to the first through fourth bankrow decoders 260 a˜260 d.

The activated one of the first through fourth bank row decoders 260a˜260 d decode the row address RA that is output from the row addressmultiplexer 240, and activates a word-line corresponding to the rowaddress RA. For example, the activated bank row decoder may apply aword-line driving voltage to the word-line corresponding to the rowaddress RA.

The column address latch 250 receives the column address COL_ADDR fromthe address register 220, and temporarily stores the received columnaddress COL_ADDR. In an embodiment, in a burst mode, the column addresslatch 250 generates column addresses that increment from the receivedcolumn address COL_ADDR. The column address latch 250 may apply thetemporarily stored or generated column addresses to the first throughfourth bank column decoders 270 a˜270 d.

The activated one of the first through fourth bank column decoders 270a˜270 d decodes the column address COL_ADDR that is output from thecolumn address latch 250, and controls the I/O gating circuit 290 tooutput data corresponding to the column address COL_ADDR.

The I/O gating circuit 290 includes a circuitry for gating input/outputdata. The I/O gating circuit 290 may further include input data masklogic, read data latches for storing data that is output from the firstthrough fourth bank arrays 310˜340, and write drivers for writing datato the first through fourth bank arrays 310˜340.

Data read from one bank array of the first through fourth bank arrays310˜340 may be sensed by sense amplifiers coupled to the one bank arrayfrom which the data is to be read, and may be stored in the read datalatches. Main data MD to be written into one bank array of the firstthrough fourth bank arrays 310˜340 may be provided to the data I/Obuffer 299 from the memory controller 100. The main data MD provided tothe data I/O buffer 299 is provided to the error correction circuit 400.The main data MD is encoded in the error correction circuit 400 togenerate a codeword CW, and the codeword CW is provided to the I/Ogating circuit 290. The write driver may write the codeword CW in onebank array of the first through fourth bank arrays 310˜340.

The data I/O buffer 299 may provide the main data MD from the memorycontroller 100 to the error correction circuit 400 in a write operationand may provide the main data MD from the error correction circuit 400to the memory controller 100 in a read operation. The data I/O buffer299 may receive the data mask signal DM from the memory controller 100and may provide the data mask signal DM to the I/O gating circuit 290.

The error correction circuit 400, in a write operation, may generateparity data based on the main data MD from the data I/O buffer 299, andmay provide the I/O gating circuit 290 with the codeword CW includingthe main data MD and the parity data. The I/O gating circuit 290 maywrite the codeword CW in one bank array.

In addition, the error correction circuit 400, in a read operation, mayreceive the codeword CW, read from one bank array, from the I/O gatingcircuit 290. In an embodiment, the error correction circuit 400 performsan ECC decoding on the main data MD based on the parity data in thecodeword CW, corrects a single bit error in the main data MD to generatecorrected main data and provides the corrected main data to the data I/Obuffer 299.

In addition, the error correction circuit 400 may perform a scrubbingoperation by reading a first unit of data from each of a pluralitysub-pages constituting each page of some pages of the memory cell array300 and perform an ECC decoding on each first unit of data sequentiallyin the ECS mode. The first unit of data includes main data and paritydata. The error correction circuit 400 may provide an error generationsignal EGS to the control logic circuit 210 when the first unit of dataincludes at least one bit error based on a result of the ECC decoding.

When the first unit of data includes at least one bit error, the controllogic circuit 210 may control the error correction circuit 400 toperform a scrubbing operation by correcting the at least one bit errorto generate corrected first unit of data and writing back the correctedfirst unit of data to a memory location corresponding to the sub-page.The control logic circuit 210 may count a number of the error generationsignal EGS and may perform an error logging operation.

The control logic circuit 210 may control operations of thesemiconductor memory device 200 a. For example, the control logiccircuit 210 may generate control signals for the semiconductor memorydevice 200 a to perform a write operation or a read operation. Thecontrol logic circuit 210 includes a command decoder 211 that decodes acommand CMD received from the memory controller 100 and a mode register212 that sets an operation mode of the semiconductor memory device 200a. The control logic circuit 210 further includes a counter 213 thatcounts the error generation signal EGS.

For example, the command decoder 211 may generate the control signalscorresponding to the command CMD by decoding a write enable signal(/WE), a row address strobe signal (/RAS), a column address strobesignal (/CAS), a chip select signal (/CS), etc. The control logiccircuit 210 may generate a first control signal CTL1 to control the I/Ogating circuit 290, a second control signal CTL2 to control the errorcorrection circuit 400 and a third control signal CTL3 to control theerror log register 460.

When the command CMD designates the ECS mode, the control logic circuit210 generates the first through third control signals CTL1, CTL2 andCTL3 such that the I/O gating circuit 290 and the error correctioncircuit 400 perform the scrubbing operation and the error loggingoperation.

In an embodiment of the inventive concept, the control logic circuit 210notifies the memory controller 100 of a first situation immediately byusing an alert signal ALRT, when the number of error occurrences (e.g.,bit errors) in one page reaches a threshold. The memory controller 100applies a scrubbing command to the semiconductor memory device 200 a inresponse to the alert signal ALRT, and the control logic circuit 210controls the I/O gating circuit 290 and the error correction circuit 400to perform the scrubbing operation on the one page. In an embodiment,the control logic circuit 210 notifies the memory controller 100 of thefirst situation by maintaining the alert signal ALRT at a logic highlevel during a first interval. For example, when the first situation isnot occurring, the control logic circuit 210 maintains the alert signalALRT at a logic low level.

When the command CMD is the scrubbing command, the command CMDconstitutes signals different from signals for a read commanddesignating a read operation or a write command designating a writeoperation of the semiconductor memory device 200 a. For example, thescrubbing command, the read command, and the write command havedifferent formats so that the command decoder 211 can distinguish themfrom one another, and operate accordingly.

FIGS. 4A to 4E are circuit diagrams of examples of the memory cell shownin FIG. 3, according to exemplary embodiments of the inventive concept.

FIGS. 4A to 4D illustrate memory cells MC which are implemented withresistive type memory cells and FIG. 4E illustrates a memory cell MCwhich is implemented with a dynamic memory cell.

FIG. 4A illustrates a resistive type memory cell without a selectionelement, while FIGS. 4B to 4D show resistive type memory cells eachcomprising a selection element.

Referring to FIG. 4A, a memory cell MC includes a resistive element REconnected to a bit-line BTL and a word-line WL. Such a resistive memorycell having a structure without a selection element may store data whena voltage is applied across the bit-line BL and the word-line WL.

Referring to FIG. 4B, a memory cell MC includes a resistive element REand a diode D. The resistive element RE may include a resistive materialfor data storage. The diode D may be a selection element (or switchingelement) that supplies current to the resistive element RE or cuts offthe current supply to resistive element RE according to a bias of aword-line WL and a bit-line BTL. The diode D is coupled between theresistive element RE and word-line WL, and the resistive element RE iscoupled between the bit-line BTL and the diode D. Positions of the diodeD and the resistive element RE may be interchanged. For example, thediode D may be connected between the resistive element RE and the bitline BTL. The diode D may be turned on or turned off by application of aword-line voltage to the word-line WL. Thus, a resistive memory cell maybe not driven when a voltage of a constant level or higher is suppliedto an unselected word-line WL.

Referring to FIG. 4C, a memory cell MC includes a resistive element REand a bidirectional diode BD. The resistive element R may include aresistive material for data storage. The bidirectional diode BD iscoupled between the resistive element RE and a word-line WL, and theresistive element RE is coupled between a bit-line BTL and bidirectionaldiode BD. Positions of the bidirectional diode BD and the resistiveelement RE may be interchanged. For example, the bidirectional diode BDmay be connected between the resistive element R and the bit-line BTL.The bidirectional diode BD may block leakage current flowing to anunselected semiconductor memory cell.

Referring to FIG. 4D, a memory cell MC includes a resistive element REand a transistor CT. The transistor CT may be a selection element (orswitching element) that supplies current to the resistive element RE orcuts off the current supply to the resistive element RE according to avoltage applied to a word-line WL. The transistor CT is coupled betweenthe resistive element RE and a word-line WL, and the resistive elementRE is coupled between a bit-line BTL and the transistor CT. Positions ofthe transistor CT and the resistive element RE may be interchanged. Forexample, the transistor CT may be connected between the resistiveelement RE and the bit line BTL. The semiconductor memory cell may beselected or unselected depending on whether the transistor CT driven byword-line WL is turned on or turned off. For example, the word-line WLis connected to a gate of the transistor CT so that a word-line voltagecan be applied to turn on or turn off the transistor CT. The transistorCT may be connected between a ground voltage and the resistive elementRE.

Referring to FIG. 4E, a memory cell MC includes a cell capacitor CC anda transistor CT. The transistor CT may be a selection element (orswitching element) that connects/disconnects a cell capacitor CC to/frombit-line BTL according to a voltage of a word-line WL. The transistor CTis coupled between the cell capacitor CC, a word-line WL and a bit-lineBTL, and the cell capacitor CC is coupled between the transistor CT anda plate voltage (not illustrated).

FIG. 5 illustrates an example of the memory cell (referred to asSTT-MRAM cell) shown in FIG. 3 according to an exemplary embodiment ofthe inventive concept.

Referring to FIG. 5, an STT-MRAM cell 30 includes a MTJ element 40 and acell transistor CT. A gate of the cell transistor CT is connected to aword-line WL and one electrode of the cell transistor CT is connectedthrough the MTJ 40 to a bit-line BTL. Also, the other electrode of thecell transistor CT is connected to a source line SL.

The MTJ element 40 includes the free layer 41, the pinned layer 43, anda tunnel layer 42 disposed between the free layer 41 and the pinnedlayer 43. A magnetization direction of the pinned layer 43 may be fixed,and a magnetization direction of the free layer 41 may be parallel to oranti-parallel to the magnetization direction of the pinned layer 43according to written data. For example, an anti-ferromagnetic layer (notshown) may be further provided to fix the magnetization direction of thepinned layer 43.

A write operation of the STT-MRAM cell 30 may be performed by applying alogic high voltage to the word-line WL to turn on the cell transistorCT. A program current, for example, a write current is applied to thebit-line BTL and the source line SL. A direction of the write current isdetermined by a logic state of the MTJ element 40.

A read operation of the STT-MRAM cell 30 may be performed by applying alogic high voltage to the word-line WL to turn on the cell transistorCT, and a read current is supplied to the bit-line BTL and the sourceline SL. Accordingly, a voltage developed at both ends of the MTJelement 40 is detected by the sense amplifier 285 a, and is comparedwith a reference voltage to determine a logic state of the MTJ element40. Accordingly, data stored in the MTJ element 40 may be detected.

FIGS. 6A and 6B illustrate a magnetization direction according to datawritten to the MTJ element shown in FIG. 5.

A resistance value of the MTJ element 40 may vary according to amagnetization direction of the free layer 41. When a read current IRflows through the MTJ 40, a data voltage is output according to theresistance value of the MTJ element 40. Since the read current IR ismuch smaller than a write current, a magnetization direction of the freelayer 41 is not changed by the read current IR.

Referring to FIG. 6A, a magnetization direction of the free layer 41 anda magnetization direction of the pinned layer 43 of the MTJ element 40are parallel. Accordingly, the MTJ element 40 may have a low resistancevalue. In this case, the MTJ element 40 may read data ‘0’.

Referring to FIG. 6B, a magnetization direction of the free layer 41 anda magnetization direction of the pinned layer 43 of the MTJ element 40are anti-parallel. Accordingly, the MTJ element 40 may have a highresistance value. In this case, the MTJ element 40 may read data ‘1’.

Although the free layer 41 and the pinned layer 43 of the MTJ element 40are horizontal magnetic layers, example embodiments are not limitedthereto and the free layer 41 and the pinned layer 43 may be, forexample, vertical magnetic layers.

FIG. 7 is a block diagram illustrating the memory controller in FIG. 2according to an exemplary embodiment of the inventive concept.

Referring to FIG. 7, the memory controller 100 includes a control logic110 (e.g., a control circuit), a register 120, a command generator 130(e.g., a circuit), a scheduler 140 (e.g., a scheduling circuit) and aninput/output (I/O) buffer 150.

The command generator 130 generates a command signal and provides thecommand signal to the scheduler 120 under control of the control logic110 such that the memory device 200 a performs active, read and writeoperations. In an embodiment, an active operation is applied to aword-line for enabling the word line to select a memory cell.

The register 120 stores an error information signal EIS received fromthe semiconductor memory device 200 a.

The control logic 110 controls the command generator 130 to generate thecommand signal based on a command signal CMD1 and an address signalADDR1 from the host 15 such that the semiconductor memory device 200 aperforms active, read and write operations. In addition, the controllogic 110 controls the command generator 130, the scheduler 140 and theI/O buffer 150 so that a scrubbing command is immediately provided tothe semiconductor memory device 200 a in response to the alert signalALRT. The control logic 110 may determine an error management policy forthe semiconductor memory device 200 a by referring to the errorinformation signal EIS stored in the register 120.

The I/O buffer 150 may temporarily store signals which are to betransmitted to the semiconductor memory device 200 a or which aretransmitted from the semiconductor memory device 200 a. Thesemiconductor memory device 200 a is connected to the I/O buffer 150through the command pin 101, the address pin 102, the data pin 103 andthe dedicated pin 104. The memory controller 100 may transmit data,address signals and operating command signals to the semiconductormemory device 200 a. For example, the memory controller 100 may transmitthe data to the semiconductor memory device 200 a through the data pin103, transmit the address signals to the semiconductor memory device 200a through the address pin 102, and transmit the operating commandsignals to the semiconductor memory device 200 a through the command pin101.

FIG. 8 illustrates a portion of the semiconductor memory device of FIG.3 in a normal mode.

In FIG. 8, the control logic circuit 210, the first bank array 310, theI/O gating circuit 290, and the error correction circuit 400 areillustrated. FIG. 8 illustrates the portion of the semiconductor memorydevice 200 a in a write operation of the normal mode.

Referring to FIG. 8, the first bank array 310 includes a normal cellarray NCA and a redundancy cell array RCA. The normal cell array NCAincludes a plurality of first memory blocks MB0˜MB15, i.e., 311˜313, andthe redundancy cell array RCA includes at least a second memory block314. The first memory blocks 311˜313 are memory blocks determining amemory capacity of the semiconductor memory device 200 a. The secondmemory block 314 is for ECC and/or redundancy repair. Since the secondmemory block 314 for ECC and/or redundancy repair is used for ECC, dataline repair and block repair to repair ‘fail’ cells (e.g., cells thathave malfunctioned) generated in the first memory blocks 311˜313, thesecond memory block 314 is also referred to as an EDB block.

In each of the first memory blocks 311˜313, a plurality of first memorycells are arranged in rows and columns. In the second memory block 314,a plurality of second memory cells are arranged in rows and columns.

In the first memory blocks 311˜313, rows may be formed, for example, of8K word-lines WL and columns may be formed, for example, of 1K bit-linesBTL. The first memory cells connected to intersections of the word-linesWL and the bit-lines BTL may be dynamic memory cells or resistive typememory cells. In the second memory block 314, rows may be formed, forexample, of 8K word-lines WL and columns may be formed, for example, of1K bit-lines BTL. The second memory cells connected to intersections ofthe word-lines WL and the bit-lines RBTL may be dynamic memory cells orresistive type memory cells.

The I/O gating circuit 290 includes a plurality of switching circuit 291a˜291 d respectively connected to the first memory blocks 311˜313 andthe second memory block 314. In the semiconductor memory device 200 a,bit lines corresponding to data of a burst length (BL) may besimultaneously accessed to support the BL indicating the maximum numberof column positions that is accessible. For example, if the BL is set to8, data bits may be set to 128 bits.

The error correction circuit 400 may be connected to the switchingcircuits 291 a˜291 d through first data lines GIO[0:127] and second datalines EDBIO[0:7].

The control logic circuit 210 may decode the command CMD to generate thefirst control signal CTL1 for controlling the switching circuits 291a˜291 d and the second control signal CTL2 for controlling the errorcorrection circuit 400.

When the command CMD is a write command, the error correction circuit400 encodes the main data MD to generate a codeword CW including themain data MD and a parity data associated with the main data MD. The I/Ogating circuit 290 stores the main data MD in the first memory blocks311˜313 and stores the parity data in the second memory block 314. Theparity data may be used to error correct the associated main data MD.

FIG. 9 illustrates a bank array and the error correction circuit shownin the semiconductor memory device of FIG. 3.

In FIG. 9, the first bank array 310 is illustrated for convenience,however, the details discussed herein related to the first bank array310 may equally apply to the other bank arrays 320, 330 and 340.

Referring to FIG. 9, each page of the first bank array 310 has a size of8 Kb and each sub-page of the page has a size of 128b. Therefore, FIG. 9illustrates 64 sub-pages. A parity data of 8b is stored for eachsub-page. Data from each sub-page of 128b and corresponding parity dataof 8b are sequentially read and provided to the error correction circuit400. A Hamming code may be used by the error correction circuit 400 forerror detection and correction. The ECC method and a codeword lengthused during read/write operations may also be used for the scrubbingoperation according to exemplary embodiments.

FIG. 10 illustrates a portion of the semiconductor memory device of FIG.3 in an ECS mode according to an exemplary embodiment of the inventiveconcept.

FIG. 10 illustrates the control logic circuit 210, the first bank array310, the I/O gating circuit 290, the error correction circuit 400, andthe error log register 460.

Referring to FIG. 10, when the command CMD designates the ECS mode, thecontrol logic circuit 210 controls the error correction circuit 400 andthe I/O gating circuit 290 to perform the ECC decoding sequentially oneach first unit of data including the main data and the parity data fromsome pages designated by the address ADDR. When the first unit of dataincludes at least one bit error based on a result of the ECC decoding,the error correction circuit 400 provides the error generation signalEGS to the control logic circuit 210.

When the first unit of data includes at least one bit error, the controllogic circuit 210 controls the error correction circuit 400 to perform ascrubbing operation by correcting the at least one bit error bit togenerate a corrected first unit of data and writing back the correctedfirst unit of data to a memory location corresponding to the sub-page.That is, the error correction circuit 400 performs the scrubbingoperation by reading a codeword RCW from a sub-page of a first page,correcting at least one bit error in the read codeword RCW to generate acorrected codeword C_CW and writing back the corrected codeword C_CWinto a memory location corresponding to the sub-page. The control logiccircuit 210 performs an error logging operation to count the errorgeneration signal EGS and to write an error information EINF into theerror log register 460. The error information EINF may include at leasta number of error occurrences on each of some pages of the memory cellarray 300.

The error information EINF may include address information ADDINF, anumber of error occurrences ECNT, ranking information RNK, a number ofsub-pages including error bits FCWCNT, flag information FG indicatingwhether the error information EINF is initially written in the error logregister 460 and change of error occurrences DINF.

In an embodiment, the control logic circuit 210 notifies the memorycontroller 100 of the first situation immediately by using an alertsignal ALRT via the pin 204. In the first situation, the number of erroroccurrences in one page reaches the threshold. The memory controller 100applies the scrubbing command to the semiconductor memory device 200 ain response to the alert signal ALRT, and the control logic circuit 210controls the I/O gating circuit 290 and the error correction circuit 400to perform the scrubbing operation consecutively on sub-pages of the onepage.

When the command CMD is a register read command RDD, the control logiccircuit 210 provides the third control signal CTL3 to the error logregister 460 such that the error information EINF in the error logregister 460 is provided to the memory controller 100 as the errorinformation signal EIS. The semiconductor memory device 200 a transmitsthe error information signal EIS to the memory controller 100 via thedata pin 203.

FIG. 11 illustrates the error log register in the semiconductor memorydevice 200 of FIG. 3 according to an exemplary embodiment of theinventive concept.

Referring to FIG. 11, each of indexes (e.g., entries) Idx1, Indx2, . . ., Idxp (p is a natural number greater than two) may include page errorinformation on each of some pages of memory cell array 300. Each entrymay correspond to one of the pages. The error log register 460 includesa plurality of columns 461, 462, 463, 464, 465, and 466. In exemplaryembodiments, one or more of the columns is omitted.

The first column 461 stores ranking information RNK on ranking of anumber of error occurrences based on the number of the error occurrencesof each of the some pages. An entry with ranking information RNK havinga lowest value (e.g., 1) could be considered a highest rank and an entrywith ranking information RNK having a highest value could be considereda lowest rank. For example, a first page associated with idx1 having 2error occurrences during a given period could receive a RNK of 2 while asecond page associated with idx2 could receive a higher RNK of 1 when ithas 4 error occurrences during the given period.

The second column 462 stores address information ADDINF of each of thesome pages. In an exemplary embodiment, the address information ADDINFincludes at least one of a bank group address (‘BGA’), a bank address(‘BA’), and a row address (‘RA’). While FIG. 3 illustrated a singlegroup of bank arrays (e.g., 310˜340), additional groups of bank arraysmay be present. The bank group address may identify one of these groups.For example, if there is a first group of bank arrays includes bankarrays 310˜340 and a second group of bank arrays, and the errors areoccurring in the first group, the BGA would identify the first group.The bank address may identify one of the banks of the identified group.The row address may identify a page of the one bank.

The third column 463 stores a number of error occurrences ECNT of eachof the some pages. For example, the error log register 460 of FIG. 11illustrates the number of error occurrences ECNT for a page havingaddress A is 2 and the number of error occurrences ECNT for a pagehaving address B is 4.

The fourth column 464 stores a number of sub-pages FCWCNT including abit error, of each of the some pages. For example, if a second page has4 bit errors (ECNT=4), the second page has 64 sub-pages, but only 3 ofthe 64 sub-pages have bit errors (e.g., sub-pages 1 and 12 each have 1bit error and sub-page 43 has 2 bit errors), the entry of the secondpage would have a FCWCNT of 3.

The fifth column 465 stores the flag information FG and the sixth column466 stores the change of error occurrences DINF of each of the somepages. The ranking information RNK indicates a ranking of a number oferror occurrences based on the number of the error occurrences of eachof the some pages. The flag information FG indicates whether the errorinformation of the corresponding page is initially written into theerror log register 460. When the error information of the correspondingpage is initially written into the error log register 460, the flaginformation FG has a first logic level (e.g., 0). In an embodiment, ifthe FG of a page has a second logic level (e.g., 1), the page previouslyhad error information.

The change of error occurrences DINF indicates an increase or a decreaseof the error occurrences in a same page between a p-th (p is a naturalnumber greater than zero) and a (p+1)-th ECS mode. For example, a DINFof 0 could indicate a decrease in error occurrences, while a DINF of 1could indicate an increase in error occurrences, over time. For example,if a first page had an ECNT of 4 at time 1 and then has an ECNT of 2 attime 2, then its entry would have a DINF of 0.

For example, the ranking information RNK of a B page whose number oferror occurrences is greatest in the p-th ECS mode has a highest rankingin the p-th ECS mode. The memory controller 100 may designate an addressof the B page such that the ECS operation is performed on the B page inthe (p+1)-th ECS mode. In the (p+1)-th ECS mode, the number of erroroccurrences ECNT in the B page increases by one, and the change of erroroccurrences DINF of the B page becomes ‘1’ in the (p+1)-th ECS mode. Thememory controller 100 accesses the error log register 460 to determinepages whose probability of error occurrence is higher than other pages.For example, even if two pages currently have a same ECNT, if a firstpage among the two pages has a DINF that indicates an increased changein error occurrences, it could be concluded that the first page has ahigher probability of error than the second page.

The some pages whose page error information is written into the errorlog register 460 may have a higher probability of error occurrence thanother pages. For example, if only pages 1-10 of a group of 12 pages havepage error information in 460, then it can be concluded that pages 1-10have a higher probability of error occurrence as compared to pages 11and 12. The some pages may be determined through testing thesemiconductor memory device 200 a or the ECS operation performed beforethe p-th ECS operation. In an embodiment, the memory controller 100accesses the error log register 460 to determine how likely pages of thememory cell array 300 are to have error occurrences and manages errorsof the semiconductor memory device 200 a based on this determination.

FIG. 12 illustrates the error correction circuit and the I/O gatingcircuit in the semiconductor memory device of FIG. 3 in the ECS modeaccording to an exemplary embodiment of the inventive concept.

Referring to FIG. 12, the error correction circuit 400 includes an ECCencoder 410 and an ECC decoder 430. The I/O gating circuit 290 includesa switching unit 291, a write driver 293 and a latch unit 295. The I/Ogating circuit 290 may further include a masking logic 296. Theswitching unit 291 may include the switches 291 a˜291 d in FIGS. 8 and10. The I/O gating circuit 290 may provide the ECC decoder 430 with theread codeword RCW read from a sub-page of a page in the memory cellarray 300 in the ECS mode. The ECC decoder 430 may correct a bit errorin the read codeword RCW using parity data in the read codeword RCW togenerate a corrected codeword C_CW and may provide the correctedcodeword C_CW to the I/O gating circuit 290. The I/O gating circuit 290receives the corrected codeword C_CW from the ECC decoder 430 and writesback the corrected data into a memory location corresponding to thesub-page. The error correction circuit 400 may provide the errorgeneration signal EGS to the control logic circuit 210 whenever an erroroccurs in the read codeword RCW while the error correction circuit 400performs the scrubbing operation.

The ECC decoder 430 may perform the above-described scrubbing operationin response to the second control signal CTL2 in the ECS mode.

FIG. 13 illustrates the error correction circuit and the I/O gatingcircuit in the semiconductor memory device of FIG. 3 in the normal mode.

Referring to FIG. 13, in a read operation of the normal mode, the I/Ogating circuit 290 provides the ECC decoder 430 with the read codewordRCW read from a sub-page of a target page in the memory cell array 300.In an embodiment, the ECC decoder 430 corrects a bit error in the readcodeword RCW using parity data in the read codeword RCW to generatecorrected main data C_MD and provides the corrected main data C_MD tothe data I/O buffer 299.

In a write operation of the normal mode, the ECC encoder 410 generatesrite parity data based on the write main data MD and provides thecodeword CW including write main data MD and the write parity data tothe I/O gating circuit 290.

The masking logic 296 controls the write driver 293 and the ECC encoder410 to perform a masked write operation in response to the data masksignal DM from the memory controller 100 in a masked write operation.

FIG. 14 illustrates that a scrubbing operation is performed in thesemiconductor memory device of FIG. 10.

Referring to FIGS. 10, 12 and 14, when the command CMD designates theECS mode, the I/O gating circuit 290 reads a first unit of codewordincluding a 64-bit first sub unit of data 511, a 64-bit second sub unitof data 513 and a 8-bit parity data PRT from a sub-page of one page inthe bank array 310 and the first unit of codeword CW is provided to theECC decoder 430 as a reference numeral indicates 521. The second subunit of data 513 includes an error bit ER. The ECC decoder 430 performsan ECC decoding on the first unit of codeword CW to detect the bit errorER, corrects the detected bit error ER in the second sub unit of data513 to generate a corrected second sub unit of data 513′ and providesthe corrected second sub unit of data 513′ to the I/O gating circuit 290as a reference numeral indicates 522. The I/O gating circuit 290 writesback the corrected second sub unit of data 513′ into a memory locationcorresponding to the second sub unit of data 513 of the sub-page as areference numeral indicates 523. In an exemplary embodiment, thescrubbing operation is performed on the one page in the bank array 310after it is determined that intensive accesses to a second page adjacentto the one page has occurred for a given time interval. For example,accesses to the second page may be considered intensive when they exceeda pre-determined rate.

FIG. 15 illustrates the ECC encoder in the error correction circuit inFIG. 13.

Referring to FIG. 15, the ECC encoder 410 includes a parity generator411. The parity generator 411 performs an ECC encoding on the write dataWMD to generate the parity data PRT in a write operation and providesthe I/O gating circuit 290 with the codeword CW including the write dataWMD and the parity data PRT.

FIG. 16 illustrates the ECC decoder in the error correction circuit inFIGS. 12 and 13.

Referring to FIG. 16, the ECC decoder 430 includes a check bit generator431, a syndrome generator 433 and a data corrector 435.

The check bit generator 431 generates check bits CHB based on the readdata RMD. The syndrome generator 433 generates a syndrome data SDR basedon the check bits CHB and the parity data PRT included in the readcodeword. The syndrome data SDR may indicate whether the read data RMDincludes at least one bit error and may also indicate a position of thebit error. The data corrector 435 may correct the bit error in the readdata RMD based on the syndrome data SDR, may provide the correctedcodeword C_CW to the I/O gating circuit 290 in a scrubbing mode and mayprovide the corrected main data C_MD to the data I/O buffer 299 in aread operation.

FIG. 17 is a flow chart illustrating a method of operating asemiconductor memory device according to an exemplary embodiment of theinventive concept.

Referring to FIGS. 2, 3, 10, 11, 12, 14, 16 and 17, in a method ofoperating a semiconductor memory device 200 a that includes a memorycell array 300, an error correction circuit 400 and an error logregister 460, the semiconductor memory device 200 a enters into an ECSmode in response to the command CMD from the memory controller 100(S510). For example, the command CMD may be received through command pin201 of the semiconductor memory device 200 a. The semiconductor memorydevice 200 a receives an address ADDR to be scrubbed simultaneously orsequentially when the semiconductor memory device 200 a enters into theECS mode (S520). The address ADDR may designate some pages of the memorycell array 300 to be scrubbed simultaneously or sequentially.

The control logic circuit 210 controls the I/O gating circuit 290 andthe error correction circuit to perform an ECS operation on a first pageof the some pages designated by the address ADDR (S600). The ECSoperation may include the ECC decoding operation and the scrubbingoperation. The ECC decoding operation may used to detect bit errors in apage of memory corresponding to the address ADDR and the scrubbingoperation may be used to correct the bit errors and write back thecorrected data to the page.

The control logic circuit 210 writes the page error information EINF ofeach of the some pages into the error log register 460 (‘ELR’) accordingto results of the ECS operation (S540). The control logic circuit 210determines whether the ECS operation has completed on all of the somepages designated by the address ADDR (S550). When the ECS operation hasnot completed on all of the some pages (NO in S550), the ECC decodingoperation and the error logging operation are performed on a second pageof the some pages. When the ECS operation has completed (YES in S550),the semiconductor memory device 200 a performs a next memory operationin response to a next command from the memory controller 100.

FIG. 18 is a flow chart illustrating the ECS operation in the method ofFIG. 17 according to an exemplary embodiment of the inventive concept.

Referring to FIGS. 3, 10, 11, 12, 14, 16, 17, and 18, at least onesub-page of the first page designated by the address ADDR is selectedand a first unit CW of data including the main data MD and the paritydata PRT is read from the selected sub-page (S610).

The ECC decoder 430 generates the syndrome data SDR (S620) to determinewhether the first unit of data CW includes a bit error (S630). Thesyndrome generator 433 generates the syndrome data SDR by checkingwhether each corresponding bit of the check bits CHB and the parity dataPRT is identical to each other. The first unit of data CW includes a biterror when at least one bit of the syndrome data SDR is not ‘0’.

When the first unit of data CW includes a bit error (YES in S630), theECC decoder 430 determines a location of at least bit one error based onthe syndrome data SDR (S640), corrects the at least one bit error basedon the parity data PRT in the first unit of data to generate a correctedcodeword C_CW (S650), and provides the corrected codeword C_CW to theI/O gating circuit 290. The I/O gating circuit 290 writes back thecorrected codeword C_CW into a memory location corresponding to thesub-page (S660).

When the first unit of data CW does not include a bit error (NO inS630), the error correction circuit 400 performs the above-describedoperation on next sub-page.

FIG. 19 is a structural diagram illustrating a semiconductor memorydevice according to an exemplary embodiment of the inventive concept.

Referring to FIG. 19, a semiconductor memory device 600 includes firstthrough kth semiconductor integrated circuit layers LA1 through Lak (kis an integer equal to or greater than three), in which the lowest firstsemiconductor integrated circuit layer LA1 is assumed to be an interfaceor control chip and the other semiconductor integrated circuit layersLA2 through LAk are assumed to be slave chips including core memorychips. The first through kth semiconductor integrated circuit layers LA1through LAk may transmit and receive signals therebetween throughthrough-silicon-vias (TSVs). The lowest first semiconductor integratedcircuit layer LA1 as the interface or control chip may communicate withan external memory controller through a conductive structure formed onan external surface. A description will be made regarding structure andan operation of the semiconductor memory device 600 by mainly using thefirst semiconductor integrated circuit layer LA1 or 610 as the interfaceor control chip and the nth semiconductor integrated circuit layer LAkor 620 as the slave chip.

The first semiconductor integrated circuit layer 610 may include variousperipheral circuits for driving memory region 621 provided in the kthsemiconductor integrated circuit layer 620. For example, the firstsemiconductor integrated circuit layer 610 may include a row (X)-driver6101 for driving word-lines of a memory, a column (Y)-driver 6102 fordriving bit-lines of the memory, a data input/output unit (Din/Dout)6103 for controlling input/output of data, a command buffer (CMD) 6104for receiving a command CMD from an outside source and buffering thecommand CMD, and an address buffer (ADDR) 6105 for receiving an addressfrom an outside source and buffering the address. The memory region 621may include a plurality of bank arrays in which a plurality of memorycells are arranged as described with reference to FIG. 3.

The first semiconductor integrated circuit layer 610 may further includea control logic (circuit) 6107. The control logic 6107 may access thememory region 621 and may generate control signals for accessing thememory region 621 based on the command from the memory controller.

The kth semiconductor integrated circuit layer 620 includes an errorcorrection circuit 622 that performs an ECC encoding on data to bestored in the memory region 621 and performs an ECC decoding on dataread from the memory region 621. The kth semiconductor integratedcircuit layer 620 further includes an error log register 623. The errorcorrection circuit 622, in the ECS mode, activates one page of thememory region 621, selects a sub-page of the activated page and performsa scrubbing operation on the activated one page to read a first unit ofdata including a main data and a parity data, to correct a bit error ofa sub-unit of data of the first unit of data to generate a correctedsub-unit of data and to write back the corrected sub-unit of data into amemory location corresponding to the sub-page.

In an embodiment, the error correction circuit 622 provides the errorgeneration signal EGS to the control logic circuit 6107 whenever anerror occurs in the first unit of data while the error correctioncircuit 400 performs the scrubbing operation. The control logic circuit6107 may performs the ECS operation on the some pages of the memoryregion 621 and may write the error information including at least thenumber of error occurrences in each of the some pages in the error logregister 623.

FIG. 20 illustrates the memory system of FIG. 2 in the ECS mode.

FIG. 21 is a flow chart illustrating a method of operating a memorysystem according to an exemplary embodiment of the inventive concept.

Referring to FIGS. 20 and 21, in the memory system 20 and in a method ofoperating a memory system, the memory controller 100 generates a command(a first command) designating the ECS mode and an address (a firstaddress) ADDR designating at least two pages to be scrubbed on thesemiconductor memory device 200 (S710). The semiconductor memory device200 enters into the ECS mode upon receipt of the first command from thememory controller 100. For example, the first command may be received bythe semiconductor memory device 200 through command pin 201.

In the ECS mode, the control logic circuit 210 controls the errorcorrection circuit 400 to perform the ECS operation including the ECCdecoding operation and the scrubbing operation on the at least two pages(S720). The error correction circuit 400 reads the first unit of datafrom each sub-page of a first page of the at least two pages, performsthe ECC decoding on the first unit of data, provides the errorgenerating signal EGS to the control logic circuit 210 when the firstunit of data includes at least one bit error, corrects the at least onebit error and writes back the corrected first unit of data into a memorylocation corresponding to the sub-page. The control logic circuit 210may write page error information in the error log register 460 while thecontrol logic circuit 210 controls the error correction 400 to performthe ECS operation on the first page.

The control logic circuit 210 controls the error correction circuit 400to perform the ECS operation on a second page of the at least two pagesafter the ECS operation on the first page has completed.

When the page error information on the at least two pages is writteninto the error log register 460, the memory controller 100 applies theregister read command to the semiconductor memory device 200 and thecontrol logic circuit 210 provides the memory controller 100 with thepage error information as the error information signal EIS in responseto the register read command (S730). The memory controller 100 mayaccess the error information in the error log register 460 and thesemiconductor memory device 200 a transmits the error information signalEIS to the memory controller 100 via the data pin 203.

While the control logic circuit 210 writes the page error information inthe error log register 460, the control logic circuit 210 may notify thememory controller 100 of a first situation immediately by activating thealert signal ALRT and outputting the activated alert signal ALRT via thepin 204 (S740). The first situation occurs when the number of erroroccurrences in at least one page reaches the threshold. The alert signalALRT may be activated by changing a level of the alert signal ALRT froma deactivated logic level to an activated other logic level, andmaintaining the activated logic level for a first time interval. Thememory controller 100 applies the scrubbing command (S750) to thesemiconductor memory device 200 a in response to the alert signal ALRT,and the control logic circuit 210 controls the I/O gating circuit 290and the error correction circuit 400 to perform the scrubbing operationconsecutively on sub-pages of the one page.

When the ECS operation has completed on the at least two pages, thememory controller 100 generates a next command for output to thesemiconductor memory device 200 a, which directs a next operation of thesemiconductor memory device 200 a (S760). If the next operation does notrelate to scrubbing, the semiconductor memory device 200 a exits the ECSmode. Alternatively, the memory controller 100 generates a command (asecond command) designating the ECS mode and an address (a secondaddress) ADDR designating at least two pages to be scrubbed on thesemiconductor memory device 200 a so the semiconductor memory device 200a can enter into the ECS mode or remain in the ECS mode.

FIG. 22 illustrates a memory system including the semiconductor memorydevice according to an exemplary embodiment of the inventive concept.

Referring to FIG. 22, a memory system 700 includes a memory module 710and a memory controller 720. The memory module 710 may include at leastone semiconductor memory devices 730 mounted on a module board. Thesemiconductor memory devices 730 may employ the semiconductor memorydevice 200 a of FIG. 3.

Therefore, each of the semiconductor memory devices 730 may include amemory cell array 731, an error correction circuit 732 and an error logregister 733. Each of the semiconductor memory devices 730 performs theECS operation on some pages of the memory cell array 731, provides thememory controller 720 with error information of each of the some pagesas an error information signal EIS and notifies the memory controller720 of a situation by using an alert signal ALRT, in which the number oferror occurrences in one page of the some pages reaches the threshold.The memory controller 720 may determine an error management policy onfault pages of each of the semiconductor memory devices 730, based onthe error information signal EIS. The fault pages may be those pagesthat include more bit error than other pages or more bit errors than areference number of bit errors. The memory controller 720 may apply thescrubbing command for a fault page to a corresponding semiconductormemory device in response to the alert signal ALRT and the correspondingsemiconductor memory device may then perform the scrubbing operation onthe corresponding fault page immediately in response the appliedscrubbing command.

In an exemplary embodiment of the present inventive concept, a threedimensional (3D) memory array is provided in semiconductor memorydevices 730. The 3D memory array is monolithically formed in one or morephysical levels of arrays of memory cells having an active area disposedabove a silicon substrate and circuitry associated with the operation ofthose memory cells, whether such associated circuitry is above or withinsuch substrate. The term “monolithic” means that layers of each level ofthe array are directly deposited on the layers of each underlying levelof the array. The following patent documents, which are herebyincorporated by reference, describe suitable configurations for the 3Dmemory arrays, in which the three-dimensional memory array is configuredas a plurality of levels, with word-lines and/or bit-lines sharedbetween levels: U.S. Pat. Nos. 7,679,133; 8,553,466; 8,654,587;8,559,235; and US Pat. Pub. No. 2011/0233648, which are herebyincorporated by reference in their entirety.

The memory module 710 may communicate with the memory controller 720 viaa system bus. Main data MD, a command/address CMD/ADDR, and a clocksignal CLK may be transmitted and received between the memory module 710and the memory controller 720 via the system bus. The semiconductormemory device 730 may transmit the error information signal EIS and thealert signal ALRT to the memory controller 720.

FIG. 23 illustrates a memory system including the semiconductor memorydevice according to an exemplary embodiment of the inventive concept.

Referring to FIG. 23, a memory system 800 includes a memory module 810and a memory controller 820. The memory module 810 may include at leastone memory chip 840 and a control chip 830. Each of the memory chips 840stores data MD based on a command CMD, an address ADDR and a clocksignal CLK and provides the data MD to the memory controller 820. Eachof the memory chips 840 may employ the semiconductor memory device 200 aof FIG. 3.

The control chip 830 may control the memory chips 840 in response tosignals from the memory controller 820. The control chip 830 mayactivate at least one of the memory chips 840 in response to a chipselection signal. The control chip 830 may include an error correctioncircuit 831 and an error log register 833. The control chip 830 mayperform an ECC decoding on the data read from each of the memory chips840. The control chip 830 performs the ECS operation on some pages inthe selected memory chip in the ECS mode and writes error information ofthe some pages in the error log register 833. The error log register 833may be assigned to each of the memory chips 840. In an embodiment, asingle error log register 833 is assigned to the memory chips 840. Whenthe single error log register 833 is assigned to the memory chips 840,the error log register 833 may include a column that stores memoryidentification information designating the selected memory chip inaddition to the information in the error log register 460 of FIG. 11.

The control chip 830 may provide the memory controller 820 with theerror information on each of the memory chips 840 with the errorinformation signal EIS. When the number of the error occurrences in theselected memory chip reaches a threshold, the control chip 830 notifiesthe memory controller 820 of the situation immediately using the alertsignal ALRT and the memory controller 820 applies the scrubbing commandto the selected memory chip immediately.

The memory controller 820 determines the error management policy of thememory chips 840 based on the error information signal EIS. When errorsin one of the memory chips 840 increases beyond the managementcapability, the memory controller 820 may chip-kill the one memory chip.In an embodiment, when errors in a first chip among the memory chips 840increases beyond the management capability, the memory controller 820replaces the first chip with an second one of the memory chips 840. Forexample, in this replacement, all data without errors and data thatcould be corrected are copied from the first chip to the second chip. Inanother embodiment, data that would normally be stored in a portion ofthe first chip that exceeds the management capability is instead storedin the second chip, and then subsequently accessed from the second chip.

FIG. 24 is a block diagram illustrating a computing system including thesemiconductor memory device (e.g., 200 a, 200, etc.) according to anexemplary embodiment of the inventive concept.

Referring to FIG. 24, a computing system 1100 includes a processor 1110,an input/output hub (IOH) 1120, an input/output controller hub (ICH)1130, at least one memory module 1140 and a graphics card 1150. In someembodiments, the computing system 1100 may be a personal computer (PC),a server computer, a workstation, a laptop computer, a mobile phone, asmart phone, a personal digital assistant (PDA), a portable multimediaplayer (PMP), a digital camera, a digital television, a set-top box, amusic player, a portable game console, a navigation system, etc.

The processor 1110 may perform various computing functions, such asexecuting specific software for performing specific calculations ortasks. For example, the processor 1110 may be a microprocessor, acentral processing unit (CPU), a digital signal processor, or the like.In some embodiments, the processor 1110 may include a single core ormultiple cores. For example, the processor 1110 may be a multi-coreprocessor, such as a dual-core processor, a quad-core processor, ahexa-core processor, etc. Although FIG. 24 illustrates the computingsystem 1100 including one processor 1110, in an embodiment, thecomputing system 1100 includes a plurality of processors. The processor1110 may include an internal or external cache memory.

The processor 1110 includes a memory controller 1111 for controllingoperations of the memory module 1140. The memory controller 1111included in the processor 1110 may be referred to as an integratedmemory controller (IMC). A memory interface between the memorycontroller 1111 and the memory module 1140 may be implemented with asingle channel including a plurality of signal lines, or may beimplemented with multiple channels, to each of which at least one memorymodule 1140 may be coupled. In an embodiment, the memory controller 1111is located inside the input/output hub 1120, which may be referred to asa memory controller hub (MCH).

The memory module 1140 may include a plurality of semiconductor memorydevices that store data provided from the memory controller 1111. Eachof the plurality of semiconductor memory devices may employ thesemiconductor memory device 200 a of FIG. 3. Therefore, each of theplurality of semiconductor memory devices may include a memory cellarray, a control logic circuit, an error correction circuit and an errorlog register as described with reference to FIGS. 2 through 19. Each ofthe semiconductor memory devices performs the ECS operation includingthe scrubbing operation and the error logging operation to provide theerror information signal EIS and the alert signal ALRT to the memorycontroller 1111. The memory controller 1111 determines the errormanagement policy of the semiconductor memory devices based on the errorinformation signal EIS.

The input/output hub 1120 may manage data transfer between the processor1110 and devices, such as the graphics card 1150. The input/output hub1120 may be coupled to the processor 1110 via various interfaces. Forexample, the interface between the processor 1110 and the input/outputhub 1120 may be a front side bus (FSB), a system bus, a HyperTransport,a lightning data transport (LDT), a QuickPath interconnect (QPI), acommon system interface (CSI), etc. Although FIG. 24 illustrates thecomputing system 1100 including one input/output hub 1120, in anembodiment, the computing system 1100 includes a plurality ofinput/output hubs.

The input/output hub 1120 may provide various interfaces with thedevices. For example, the input/output hub 1120 may provide anaccelerated graphics port (AGP) interface, a peripheral componentinterface-express (PCIe), a communications streaming architecture (CSA)interface, etc.

The graphics card 1150 may be coupled to the input/output hub 1120 viaAGP or PCIe. The graphics card 1150 may control a display device (notshown) for displaying an image. The graphics card 1150 may include aninternal processor for processing image data and an internalsemiconductor memory device. In an embodiment, the input/output hub 1120includes an internal graphics device along with or instead of thegraphics card 1150 disposed outside the input/output hub 1120. Thegraphics device included in the input/output hub 1120 may be referred toas integrated graphics. Further, the input/output hub 1120 including theinternal memory controller and the internal graphics device may bereferred to as a graphics and memory controller hub (GMCH).

The input/output controller hub 1130 may perform data buffering andinterface arbitration to efficiently operate various system interfaces.The input/output controller hub 1130 may be coupled to the input/outputhub 1120 via an internal bus, such as a direct media interface (DMI), ahub interface, an enterprise Southbridge interface (ESI), PCIe, etc. Theinput/output controller hub 1130 may provide various interfaces withperipheral devices. For example, the input/output controller hub 1130may provide a universal serial bus (USB) port, a serial advancedtechnology attachment (SATA) port, a general purpose input/output(GPIO), a low pin count (LPC) bus, a serial peripheral interface (SPI),PCI, PCIe, etc.

In an embodiment, the processor 1110, the input/output hub 1120 and theinput/output controller hub 1130 are implemented as separate chipsets orseparate integrated circuits. In an embodiment, at least two of theprocessor 1110, the input/output hub 1120 and the input/outputcontroller hub 1130 are implemented as a single chipset.

Aspects of the present inventive concept may be applied to systems usingsemiconductor memory devices. For example aspects of the presentinventive concept may be applied to systems such as be a mobile phone, asmart phone, a personal digital assistant (PDA), a portable multimediaplayer (PMP), a digital camera, a camcorder, personal computer (PC), aserver computer, a workstation, a laptop computer, a digital TV, aset-top box, a portable game console, a navigation system, or other suchelectronic devices.

The foregoing is illustrative of exemplary embodiments and is not to beconstrued as limiting thereof. Although a few example embodiments havebeen described, those skilled in the art will readily appreciate thatmany modifications are possible in the exemplary embodiments withoutmaterially departing from the present inventive concept. Accordingly,all such modifications are intended to be included within the scope ofthe present inventive concept.

What is claimed is:
 1. A semiconductor memory device comprising: amemory cell array including a plurality of memory bank arrays, whereineach memory bank array includes a plurality of memory cell rows; anerror correction circuit; an error log register; and a control logiccircuit configured to control the error correction circuit to perform anerror correction code (ECC) decoding sequentially on some of the memorycell rows designated by at least one internally generated address fordetecting at least one bit error in each of the some memory cells, inresponse to a first command from a memory controller in an error checkand scrub (ECS) mode, wherein the control logic circuit is configured toperform an error logging operation to write error information into eachrow of the error log register, and wherein the error informationincludes a number of error occurrence count for each of the some memorycell rows, which is determined by the control logic circuit.
 2. Thesemiconductor memory device of claim 1, wherein the control logiccircuit is configured to control the error correction circuit to read acodeword unit of data from each of a plurality memory locations in afirst memory cell row of the some memory cell rows and to perform theECC decoding on each codeword unit of data sequentially, the codewordunit of data including a main data and a parity data, and wherein theerror correction circuit is configured to provide an error generationsignal to the control logic circuit when the codeword unit of dataincludes at least one bit error based on a result of the ECC decoding.3. The semiconductor memory device of claim 2, wherein when the codewordunit of data includes the at least one bit error, the control logiccircuit is configured to control the error correction circuit to performa scrubbing operation to correct the at least one bit error and writeback the corrected codeword unit of data to a memory location in whichthe codeword unit of data is stored.
 4. The semiconductor memory deviceof claim 2, wherein the control logic circuit is configured to count anumber of the error generation signals received to write a first rowerror information into the error log register and the first row errorinformation includes a number of error occurrence in the first page. 5.The semiconductor memory device of claim 2, wherein when the errorlogging operation on the first memory cell row has completed, thecontrol logic circuit is configured to control the error correctioncircuit to perform the ECC decoding operation on a second memory cellrow of the some memory cell rows, and the control logic circuit isconfigured to write second row error information into the error logregister and the second row error information includes a number of erroroccurrence in the second memory cell row.
 6. The semiconductor memorydevice of claim 1, wherein the control logic circuit is configured tonotify the memory controller when the number of error occurrences in onememory cell row of the some memory cell has reached a thresholdimmediately by using an alert signal, the memory controller isconfigured to apply a scrubbing command to the semiconductor memorydevice in response to the alert signal, and the control logic circuit isconfigured to control the error correction circuit to perform thescrubbing operation on the one page.
 7. The semiconductor memory deviceof claim 6, wherein the control logic circuit is configured to maintainthe alert signal at a logic high level during a first interval when theoccurrence count in the one page has reached the threshold.
 8. Thesemiconductor memory device of claim 6, wherein the control logiccircuit is configured to transmit the alert signal to the memorycontroller via a dedicated pin.
 9. The semiconductor memory device ofclaim 6, wherein the control logic circuit is configured to control theerror correction circuit to perform the scrubbing operation sequentiallyon codeword units of data of the one memory cell row, in response to thescrubbing command.
 10. The semiconductor memory device of claim 1,wherein the error log register includes: a first column that storesaddress information of each of the some memory cell rows; a secondcolumn that stores a number of error occurrence of each of the somememory cell rows; a third column that stores a number of codewordsincluding the at least one bit error, of each of the some memory cellrows; a fourth column that stores flag information indicating whethererror information of each of the some memory cell rows is initiallywritten to a fifth column that stores a ranking information on rankingof a number of error occurrences based on the number of the erroroccurrences of each of the some memory cell rows.
 11. The semiconductormemory device of claim 10, wherein the address information includes abank group address, a bank address and a row address of each of the somememory cell rows, which are internally generated in the semiconductormemory device.
 12. The semiconductor memory device of claim 10, whereinthe control logic circuit includes: a first counter configured to counta number of codewords including the at least one bit error, of each ofthe some memory cell rows; and a second counter configured to count anumber of error occurrence of each of the some memory cell rows.
 13. Thesemiconductor memory device of claim 12, wherein the first counterresets when a codeword address designating a codeword unit of datareaches a first maximum value, and wherein the second counter resetswhen a bank group address reaches a second maximum value.
 14. Thesemiconductor memory device of claim 1, wherein the first command is anECS entry command designating the ECS mode.
 15. The semiconductor memorydevice of claim 1, wherein the control logic circuit is configured toprovide the memory controller with the error information of the somememory cell rows in the error log register as an error informationsignal, in response to a read command from the memory controller.
 16. Amemory system comprising: the semiconductor memory device of claim 1;and a memory controller, wherein the memory controller is configured tocontrolhe semiconductor memory device.
 17. A method of operating amemory system including a semiconductor memory device and a memorycontroller configured to control the semiconductor memory device, themethod comprising: generating, in the memory controller, an error checkand scrub (ECS) entry command; performing, by the semiconductor memorydevice, an error correction code (ECC) decoding sequentially on somememory cell rows of the semiconductor memory device designated by atleast an internally generated address for detecting at least one biterror in each of the some memory cell rows, in response to the ECS entrycommand in an ECS mode; determining, by a control circuit in thesemiconductor memory device, an error occurrence count for each of thesome memory cell rows based on a number of the corresponding detected atleast one bit error; and performing, by the semiconductor memory device,an error logging operation to write error information into an error logregister, the error information including the error occurrence count foreach of the some memory cell rows.
 18. A semiconductor memory devicecomprising: a memory cell array; a register storing error occurrencecounts for each memory cell row of a plurality of memory cell rows ofthe memory cell array, where each stored error occurrence count is basedon at least one error bit that occurred in a corresponding one of thememory cell rows; and a controller configured to receive a commandthrough a first pin of the semiconductor memory device, receive anaddress through a second pin of the semiconductor memory device,exchange data through a third pin of the semiconductor memory deviceduring a first mode, and output a signal including information of theregister through the third pin to a memory controller during a secondother mode.
 19. The semiconductor memory device of claim 18, wherein thecontroller performs an error correction code (ECC) decoding on some ofthe memory cell rows designated by an internally generated address fordetecting at least one bit error, in response to the command, and writeserror occurrence counts determined from the detecting into the registerin the second other mode, wherein the second command is an error checkand scrub (ECS) entry command designating the second other mode, and thesecond other mode corresponds to an ECS mode.